He has a sworn statement of the accuser she was raped by three guys at the house, he has the SANE nurse examination "consistent with" rape and he has photo identification of the two suspects (plus the towel if it is those two).
The defense does not get to present their side to the GJ, so that is probably sufficient to get a true bill, and therefore Nifong accomplishing something before the election.
Reminds me of an old saying. 90% of men admit to occasional self-pleasuring; and the other 10% are lying.